🦋 Swift — Learn From Zero

Playground: Swift Playgrounds | Replit Swift — click, type, run.

What is Swift?

Swift is Apple's fast, safe language for iOS, macOS, and server-side. Modern syntax with strong type safety.

iOS & macOS apps
Server (Vapor)
Systems scripting
ML with Core ML

Run Online — No Install

Use the playground links above.

🟢 Beginner — Core Basics

Your First Program

swift

print("Hello, world!")

No main needed in a playground.

Variables & Types

swift

let name = "Ada"
var age = 36
let height: Double = 1.78

Use let (constant) by default.

If / Else

swift

let age = 18
if age >= 18 {
  print("Vote")
} else {
  print("Too young")
}

Conditionals don't need parens.

Loops

swift

for i in 0..<5 { print(i) }
for fruit in ["apple", "banana"] { print(fruit) }

Use 0..<5 (half-open).

Functions

swift

func greet(_ name: String) -> String {
  return "Hello, \(name)!"
}

String interpolation with \().

Optionals

swift

var s: String? = nil
if let val = s { print(val) }
print(s?.count ?? 0)

? marks optional; unwrap safely.

🟡 Intermediate — Building Real Programs

Structs & Classes

swift

struct Person {
  var name: String
  var age: Int
}

Value types (struct) vs reference (class).

Protocols

swift

protocol Animal { func speak() }
struct Dog: Animal { func speak() {} }

Protocols are interfaces.

Closures

swift

let add: (Int, Int) -> Int = { $0 + $1 }
print(add(2, 3))

Trailing closures & shorthands.

Enums

swift

enum Direction { case north, south }
let d = Direction.north
switch d { case .north: break; default: break }

Powerful enums with associated values.

Collections

swift

let nums = [1, 2, 3]
let even = nums.filter { $0 % 2 == 0 }

Functional methods on collections.

🔴 Advanced — Pro Concepts

async/await

swift

func load() async -> String {
  try? await Task.sleep(nanoseconds: 1_000_000_000)
  return "x"
}

Swift Concurrency model.

Generics

swift

func first(_ arr: [T]) -> T? { arr.first }

Type parameters.

Property Wrappers

swift

@propertyWrapper
struct Clamped { var wrappedValue: Int { didSet { } } }

Reusable property logic.

Actors

swift

actor Bank {
  var balance = 0
  func deposit(_ n: Int) { balance += n }
}

Data-race safety for concurrency.

What's Next?

Build a tiny project: Calculator, To-Do App, Weather Widget
Read the official docs and a good book
Solve Exercism exercises
Join a community & share your code

Practice daily for 20 minutes. Consistency > intensity.